Preparation process of high-content 2, 4-D

Abstract

The invention discloses a preparation process of high-content 2, 4-D, which can be used for preparing a high-content 2, 4-D product with the purity of more than 98.5%. The process comprises the following steps: dissolving 2, 4-D sodium salt, adsorbing, removing impurities and decolorizing, acidifying, extracting, crystallizing and the like. The conversion technology provided by the invention can realize preparation of high-content 2, 4-D at high temperature and normal pressure, so that the content of 2, 4-D reaches 98.5% or above, the influence of impurities on the quality of products such as 2, 4-D dimethylamine salt and 2, 4-D isooctyl ester prepared downstream is effectively avoided, and the product quality and customer satisfaction are improved.

Description

Technical Field

[0001] The present invention relates to the field of synthetic preparation technology of 2,4-D, and more specifically to the field of preparation technology of high-content 2,4-D. Background Art

[0002] 2,4-D is a phenoxycarboxylic acid herbicide. Some people call it "kill grass quick" and "soybean joy". Its chemical name is 2,4-dichlorophenoxyacetic acid. It has dual uses. It can be used as a herbicide and a plant growth regulator. It is a common auxin that induces the formation of wound tissue healing in crops. It is absorbed into the plant body through the roots, stems and leaves. It is metabolized slowly and can accumulate to a certain concentration, thereby interfering with the balance of active elements in the plant body and destroying protein and nucleic acid metabolism. It can inhibit or promote the growth of certain organs of the plant, causing the weed stem base to become thicker, the leaf stem to twist, and the swelling and rupture. It is mainly used to control dicotyledonous broad-leaved weeds and budding grass weeds in the fields of monocotyledonous crops such as rice, wheat and corn. Domestic production factories include Nantong Taihe Chemical Co., Ltd., Shandong Keyuan Chemical Co., Ltd., Weihai Hanfu Biochemical Pharmaceutical Co., Ltd., Shandong Weifang Runfeng Chemical Co., Ltd., and Hubei Xingchen Technology Co., Ltd. The market demand is about 130,000 tons per year. The synthetic route of 2,4-D usually uses phenol chlorination to produce 2,4-dichlorophenol, which is condensed with chloroacetic acid in the presence of sodium hydroxide to produce 2,4-D sodium salt, and then acidified to produce 2,4-D technical.

[0003] In the prior art, whether the production process is chlorination followed by etherification or etherification followed by chlorination, the content of 2,4-D technical drug can reach above 97.5%. However, due to the low level of equipment automation control and backward production process, the content of free phenol and sodium ion in 2,4-D technical drug exceeds the standard. When the 2,4-D technical drug with excessive free phenol and sodium ion content is used in downstream preparations and 2,4-D isooctyl ester synthesis, it is easy to cause product crystallization and color instability in the downstream. Therefore, how to prepare high-content and low-impurity 2,4-D technical drug through process adjustment is a bottleneck problem that the 2,4-D industry urgently needs to solve. Summary of the invention

[0004] Therefore, the present invention proposes a preparation process for high-content 2,4-D, which realizes the preparation of high-content 2,4-D at high temperature and normal pressure through processes such as 2,4-D sodium salt dissolution, adsorption and decolorization, acidification and extraction crystallization, and effectively avoids the influence of impurities on the quality of downstream products such as 2,4-D dimethylamine salt and 2,4-D isooctyl ester.

[0005] The above processing method comprises the following steps: Add a certain amount of soft water to the 2,4-D sodium salt obtained by the condensation reaction, heat it up to dissolve it, the mass ratio of the 2,4-D sodium salt to the soft water is 1:1.5-1:3, and the dissolution temperature is controlled at 40-80°C to obtain a 2,4-D sodium salt solution.

[0006] The obtained 2,4-D sodium salt solution is subjected to primary adsorption, and the impurity components are removed by adsorption with an adsorbent to obtain a 2,4-D sodium salt primary refined solution; the 2,4-D sodium salt primary refined solution is subjected to secondary adsorption to obtain a 2,4-D sodium salt secondary refined solution, which is sent to an acidification kettle for 2,4-D synthesis.

[0007] The adsorption process includes primary adsorption and secondary adsorption. The primary adsorbent is solid adsorbent 1. The solid adsorbent 1 includes the following raw materials based on the total mass percentage of 100%: filler 0-4% and activated carbon 60-100%.

[0008] The secondary adsorbent is solid adsorbent 2, and the solid adsorbent 2 includes the following raw materials, based on the total mass percentage of which is 100%: filler 0-30% and macroporous resin 70-100%.

[0009] The fillers are ceramic structured fillers and ceramic Raschig ring fillers, and the macroporous resin is a polystyrene polymer with a particle size of 20-80 mesh and a specific surface area of ​​1000-2000 m 2 / g, the primary adsorption temperature is 15-60℃, and the secondary adsorption temperature is 10-80℃.

[0010] Hydrochloric acid (the mass concentration of the hydrochloric acid is 31-35%) is added dropwise to the refined solution of 2,4-dichlorophenoxyacetic acid sodium salt after the secondary adsorption until the pH value is 0.5-2, and an acidification reaction is carried out at a temperature of 80-115°C.

[0011] The reaction solution of the acidified reaction solution is cooled, and then a certain amount of extractant is added for extraction, and then cooled, crystallized, centrifuged and dried to obtain a high-content 2,4-D product. The extractant is one of ethanol, benzene, acetone, toluene, acetic acid, methyl isopropyl ketone, xylene, trimethylbenzene, etc. or any combination of two. The mass ratio of the acidified 2,4-dichlorophenoxyacetic acid refined solution to the extractant is 1:0.3-0.8.

[0012] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages: (1) The present invention is simple to operate, has mild conditions, rapid reaction, is easy to automate, can be mass-produced and applied, and has good application prospects.

[0013] (2) The raw materials of the present invention (both the acid and the base are basic chemical raw materials) are widely available and inexpensive, and the extraction solvent can be further reused or recycled, thus having good economic benefits.

[0014] (3) The present invention simply adds adsorption and extraction processes to the original process without affecting the original production efficiency. It cleverly utilizes the characteristics that phenolic substances are easily adsorbed by macroporous resins, and the characteristics that phenolic substances are soluble in extractants, 2,4-D sodium salt is soluble in extractants, and 2,4-D is slightly soluble in water, thereby effectively removing free phenol in 2,4-D original drug and improving product quality. DETAILED DESCRIPTION

[0015] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments. However, the following embodiments are merely illustrative, and the present invention is not limited to these embodiments.

[0016] The 2,4-D sodium salt described in the present invention is a 2,4-D sodium salt prepared by chlorination followed by condensation (the preparation method is the same as the preparation process for catalytic synthesis of 2,4-D in patent document CN116120168B. To avoid repeated description, this case only uses Example 1 of the modified patent as the next step of the experiment in this case).

[0017] Example 1 The preparation process of high-content 2,4-D described in this embodiment comprises the following steps: (1) Dissolution of sodium salt: Add a certain amount of soft water to the 2,4-D sodium salt obtained by the condensation reaction, stir and heat to dissolve, and obtain a 2,4-D sodium salt solution. The mass ratio of 2,4-D sodium salt to soft water is 1:1.5, and the dissolution temperature is controlled at 60°C.

[0018] (2) Adsorption and decolorization: 2,4-D sodium salt solution is subjected to primary adsorption, and impurity components are removed by adsorption by adsorbent to obtain a 2,4-D sodium salt primary refined solution; the 2,4-D sodium salt primary refined solution is subjected to secondary adsorption to obtain a 2,4-D sodium salt secondary refined solution, which is sent to the acidification kettle. The primary adsorption temperature is 60°C, and the secondary adsorption temperature is 80°C. Solid adsorbent 1, calculated by the total mass percentage content as 100%, includes the following raw materials: filler 40% (ceramic material regular filler), activated carbon 60%, solid adsorbent 2, calculated by the total mass percentage content as 100%, includes the following raw materials: filler 30% (ceramic material Raschig ring filler), macroporous resin 70%, the macroporous resin is a polystyrene polymer with a particle size of 20~80 mesh and a specific surface area of ​​1000-2000 m 2 / g.

[0019] (3) Acidification: Add 31% hydrochloric acid to the purified solution of 2,4-dichlorophenoxyacetic acid sodium salt after the secondary adsorption until the pH value is 0.5, and carry out acidification reaction at a temperature of 95°C.

[0020] (4) Extraction and crystallization: Then add an extractant for extraction, the mass ratio of 2,4-dichlorophenoxyacetic acid refined solution to the extractant is 1:0.5, and then cool, crystallize, centrifuge and dry to obtain a high-content 2,4-D product, and the extractant is 60% dilute acetic acid.

[0021] The 2,4-D (2,4-dichlorophenoxyacetic acid) content obtained after drying was 98.9%, the free phenol content was 0.005%, and the sodium ion content was 268 ppm.

[0022] Example 2 (Extraction agent: benzene) The method and conditions were the same as in Example 1, except that the extractant was replaced by benzene.

[0023] The 2,4-D (2,4-dichlorophenoxyacetic acid) content obtained after drying was 98.1%, the free phenol content was 0.016%, and the sodium ion content was 657 ppm.

[0024] Example 3 (the acidification pH value is controlled at 2, and the acidification temperature is controlled at 85°C) The method and conditions were the same as those in Example 1, except that the acidification pH value was controlled at 2 and the acidification temperature was controlled at 85°C.

[0025] The 2,4-D (2,4-dichlorophenoxyacetic acid) content obtained after drying was 97.3%, the free phenol content was 0.13%, and the sodium ion content was 2187 ppm.

[0026] Example 4 (2,4-drop sodium salt solution undergoes only one-stage adsorption) The method and conditions are the same as in Example 1, except that the 2,4-D sodium salt solution undergoes only one-stage adsorption.

[0027] The 2,4-D (2,4-dichlorophenoxyacetic acid) content obtained after drying was 97.8%, the free phenol content was 0.22%, and the sodium ion content was 293 ppm.

[0028] Example 5 (mass ratio of 2,4-dichlorophenoxyacetic acid purified solution to extractant 1:0.3) The method and conditions are the same as those in Example 1, except that the mass ratio of the 2,4-dichlorophenoxyacetic acid refined solution to the extractant is 1:0.3.

[0029] After drying, the 2,4-D (2,4-dichlorophenoxyacetic acid) content was 98.3%, the free phenol content was 0.015%, and the sodium ion content was 326 ppm.

[0030] Example 6 (Solid adsorbent 2 is 60% Raschig ring filler and 40% macroporous resin) The method and conditions are the same as in Example 1, except that the solid adsorbent 2 is 60% Raschig ring filler and 40% macroporous resin.

[0031] The 2,4-D (2,4-dichlorophenoxyacetic acid) content obtained after drying was 98.1%, the free phenol content was 0.022%, and the sodium ion content was 335 ppm.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can make appropriate modifications to the technical cases described in the above embodiments. However, the modified parts cannot deviate from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. A process for preparing high-content 2,4-D, characterized in that: The following steps are involved: S1: adding a certain amount of soft water to the 2,4-D sodium salt obtained by the condensation reaction, heating and dissolving the mixture to obtain a 2,4-D sodium salt solution; S2: subjecting the 2,4-D sodium salt solution obtained in step 1 to primary adsorption, removing impurity components through adsorption by an adsorbent, and obtaining a 2,4-D sodium salt primary refined solution; subjecting the 2,4-D sodium salt primary refined solution to secondary adsorption to obtain a 2,4-D sodium salt secondary refined solution, which is sent to an acidification kettle for 2,4-D synthesis; The adsorption process includes primary adsorption and secondary adsorption. The adsorbent of the primary adsorption is solid adsorbent 1. The solid adsorbent 1 includes the following raw materials based on the total mass percentage of 100%: filler 0-40%, activated carbon 60-100%; The adsorbent for secondary adsorption is solid adsorbent 2, and the solid adsorbent 2, calculated based on the total mass percentage content being 100%, includes the following raw materials: filler 0-30%, macroporous resin 70-100%; S3: adding hydrochloric acid dropwise to the purified solution of 2,4-dichlorophenoxyacetic acid sodium salt after the secondary adsorption until the pH value is 0.5-2, and performing an acidification reaction at a temperature of 80-115°C; S4: Cooling the reaction solution of step S3, then adding an extractant for extraction, and then cooling, crystallizing, centrifuging and drying to obtain a high-content 2,4-D product.

2. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The mass ratio of 2,4-D sodium salt to soft water is 1:1.5-1:3, and the dissolution temperature is controlled at 40-80℃.

3. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The primary adsorption temperature is 15-60℃.

4. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The secondary adsorption temperature is 10-80℃.

5. A process for preparing a high content of 2,4-D according to claim 1, characterized in that Macroporous resin is a polystyrene polymer with a particle size of 20-80 mesh and a specific surface area of ​​1000-2000 m 2 / g.

6. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The filler in the solid adsorbent 1 is a ceramic structured filler; the filler in the solid adsorbent 2 is a ceramic Raschig ring filler.

7. A process for preparing high-content 2,4-D according to claim 6, characterized in that: The packing is a structured packing, a Raschig ring packing or a Pall ring packing.

8. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The extractant is one of ethanol, benzene, acetone, toluene, acetic acid, methyl isopropyl ketone, xylene, trimethylbenzene, etc., or a combination of any two thereof.

9. A process for preparing high-content 2,4-D according to claim 1, characterized in that: The mass ratio of the acidified 2,4-dichlorophenoxyacetic acid refined solution to the extractant is 1:0.3-0.8.